Yard marker / stake / button thing

I needed a way to mark something in my yard on a semi permanent basis, that would survive the lawnmower. So I'm not sure what to call this, but I drew this little coin/stake marker thing that you can just push into the ground. it only sits 2mm above the ground, not high enough to hit the lawnmower blade. EDIT - the smaller disc version got lost in the long grass, so I made a larger disc version (double the size). I added that file here as well.